MRI-TRUS fusion biopsy of the prostate: Quality of image fusion in a clinical setting

Abstract

Introduction: Prostate cancer (PCa) is one of the most common malignancies in men. The diagnostic standard to confirm prostate cancer is the transrectal ultrasound-guided biopsy. However, this procedure is associated with the underdetection of clinically significant prostate cancer and therefore needs to be improved. In the last years MRI fusion based targeted biopsy gained importance as consequence. In this study, we evaluated the quality of MRI ultrasound image fusion and evaluated factors influencing the image fusion quality. This was done by comparing fusion quality with the histopathological findings in the defined MRI target on the one hand and the PIRADS score on the other hand.

Materials and methods: Single arm study including patients with elevated prostate specific antigen (PSA) and a multiparametric MRI showing a suspicious lesion underwent a MRI fusion targeted biopsy at our institution. MRI fusion targeted biopsy and an additional 12-core transrectal ultrasound (TRUS) guided biopsy was performed using the Philips Percunav device (Philips Medical Systems, Bothell, WA). The fusion accuracy was rated by two experienced clinicians (1 radiologist, 18 years of experience, 1 urologist, 5 years of experience) using a five-point rank scale (1 = best) and comparing the result with the histological findings in the target and the PIRADS score.

Results: The detection rate of clinically significant cancer (Gleason 7a or greater) by MRI-ultrasound fusion targeted biopsy was 58.6% (17/29) compared to 50% (19/38) in the standard transrectal ultrasound-guided approach. PCa was found in 36.4% (4/11 patients) of patients with a PIRADS 3 lesion, in 57.7% (15/26 patients) of patients with a PIRADS 4 lesion. In 76.9% (10/13 patients) of patients with a PIRADS 5 lesion PCa was diagnosed. No statistical significance was found comparing the quality of registration either with the PIRADS (p = 0.7873) nor with the Gleason score (p = 0.4376). The study is limited by the small number of patients.

Conclusions: MRI fusion based targeted biopsy improves the identification of clinical significant cancer. The Gleason score of detected PCa is not influenced by the quality of fusion.

Keywords: Transrectal ultrasound-guided biopsy; image fusion; multiparametric MRI; prostate; prostate cancer.